ubuntu shows it both uses mesa and VBoxOGL as libGL.so.1

[MounTainLion]

Hi!
I'm running ubuntu on virtualbox.
I installed guest addition on my ubuntu and wonder that this addition really works.

so I use ldconfig to find ld configuration

Code: Select all

~$> ldconfig -p
...
	libGL.so.1 (libc6,x86-64) => /tmp/VBoxOGL/libGL.so.1
	libGL.so.1 (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/mesa/libGL.so.1
	libGL.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/libGL.so
	libGL.so (libc6,x86-64) => /usr/lib/x86_64-linux-gnu/mesa/libGL.so
...

libGL is pointing both mesa and VBoxOGL, how does my ubuntu guest knows that it will use VBoxOGL as a libGL.so?
how does such priority is defined?